The human liver serves as the reservoir for several important pathogens, including hepatitis B (HBV) and C viruses (HCV) and the malaria parasites, all of which represent serious global health problems. Chronic infections with HCV alone affect an estimated 130 million people. Persistent HCV infection can have severe health consequences, including hepatitis, cirrhosis, liver failure, and hepatocellular carcinoma. This virus is associated with more than half of newly diagnosed hepatocellular carcinomas in the United States and is currently the leading indicator for liver transplantation worldwide. No HCV vaccine exists and treatment options are limited and only 50% in genotype 1-infected patients and even less effective in certain patient populations. Currently, HCV-associated liver transplantation is merely a palliative procedure due to universal re-infection of the graft, often resulting in rapid fibrosis progression and subsequent graft failure. Clinical data demonstrate that cure of HCV infection can be achieved, but, due to the remarkable replicative capacity of the virus and its error-prone polymerase, antiviral resistance is a major problem. A number of HCV proteins may serve as viable drug targets, but pre- and early clinical data highlight the dangers of mono-therapy, as was observed in early HIV drug trials. Development of more effective therapies, including a preventative or therapeutic vaccine has been severely hampered by the lack of suitable animal models for HCV infection. Chimpanzees, currently the only available immunocompetent in vivo experimental system, are limited due to ethical concerns, restricted availability and prohibitively high costs. To address this need, we propose to systematically identify and overcome blocks in the HCV life-cycle in non-human primate cells. Our long-term goal is to adapt HCV to infect a small non-human primate, creating a simian tropic HCV (stHCV) strain. Although, others have failed in this endeavor, several recent advances justify optimism for our success. HCV can now be readily propagated in immortalized cell lines and primary cultures, facilitating isolation and characterization of simian-tropic strains. In addition, our own studies have provided valuable insights into the determinants of species tropism at the level of virus entry. Here, we propose to exploit the highly error-prone nature of HCV replication, which leads to expansive sequence diversity and the potential for rapid increases in replicative fitness, to adapt the virus to growth in simian cells. As a host species, we will initially focus on Rhesus macaques (Macaca mulatta) - monkeys that can be bred in captivity, have sufficient available research tools, are readily obtainable, can be used for terminal experiments, and are cost effective for experiments with larger cohorts. If HCV cannot be adapted to this species we will test other non-human primate species for their abilities to support the HCV life- cycle. The development of a small-primate host for HCV would have enormous utility in drug and vaccine development, and could also serve to model common clinical complications including HCV/HIV co-infection. PUBLIC HEALTH RELEVANCE: Hepatitis C virus (HCV) is a leading cause of liver disease including cancer. This proposal aims to create a non-human primate model for HCV infections. Such an animal model for this human pathogen would open new avenues to develop more effective treatments aimed at eradicating this deadly viral disease.